Julian Nagelsmann's side are yet to take to the field this summer, while the Washington outfit last suffered a 2-0 defeat to Minnesota United.
Match preview
Rooney spent very little of his playing career down in the lower half of the league table, but the former Manchester United and England striker is now desperately trying to find the formula to lift DC United off the bottom of the Eastern Conference standings.
For the time being, Chad Ashton remains in interim charge of DC United, where Rooney enjoyed a brief but goal-laden stint as a player, but his side succumbed to a double from Emanuel Reynoso in a 2-0 loss to Minnesota United at the weekend.
With a Conference-high 41 goals shipped in 19 matches so far, DC United sit 14th in the standings but do possess two games in hand over Toronto and Chicago Fire, who are one and five points clear of the basement outfit respectively.
Shoring up a defence that has conceded 17 goals in their last five MLS encounters will be a tall order for Rooney, and a DC side who have not won at home in MLS since May ought to be grateful that Bayern's second-highest goalscorer of all time has ended his stint in Bavaria.
After eight years of service, 344 goals and countless pieces of silverware, Bayern Munich ultimately relented and allowed Robert Lewandowski to complete his desired switch to Barcelona before losing him on a free transfer in 2023.
Oliver Kahn and Hasan Salihamidzic repeatedly insisted that Lewandowski would honour the final year of his contract at the Allianz Arena, but Bayern chiefs may very well have just been creating a smokescreen, and receiving £42.5m for a 33-year-old is not bad going indeed.
Defending their status as perennial Bundesliga champions will not be so easy without Lewandowski in the ranks, but Julian Nagelsmann's side have made notable improvements in all areas of the field as they endeavour to win Germany's top prize for an 11th year running.
Noussair Mazraoui, Ryan Gravenberch and Sadio Mane will don the Bavarian shade of red for the 2022-23 season, and the club have also cut numerous players from their wage bill, allowing Marc Roca, Corentin Tolisso, Niklas Sule and Omar Richards to seek pastures new.
A heavyweight showdown with Manchester City takes place three days after the meeting with DC United for Bayern, who must now prove their worth without the prolific Pole Lewandowski scoring at least 40 goals a season.
DC United form (all competitions):
Team News
DC United's treatment room is at near full-capacity at the minute, with Ola Kamara, Brad Smith, Adrien Perez and Bill Hamid all guaranteed to miss the friendly showdown with Bayern.
Tony Alfaro is unlikely to be risked either, while English attacker Kimarni Smith was only on the field for 45 minutes against Minnesota and Julian Gressel has been offloaded to Vancouver.
On a brighter note, midfielder Russell Canouse was fit enough to play the final 10 minutes of Saturday's defeat, but top scorer Taxiarchis Fountas is nursing a minor injury and Martin Rodriguez is yet to receive his visa.
Meanwhile, Bayern fans should witness Mane make his debut for the club on Wednesday night, but the ex-Liverpool man will then temporarily leave the camp to attend the CAF Awards before returning to the States.
Barring any late injuries, Nagelsmann will be working with a fully-fit squad for Wednesday's game, and the club are also said to be closing in on the signing of Dutch defender Matthijs de Ligt from Juventus.
The 22-year-old is unlikely to arrive in time to make his debut on Wednesday night, leaving Lucas Hernandez and Dayot Upamecano to partner up at the back.
DC United possible starting lineup:
Romo; Durkin, Birnbaum, Hines-Ike, Guediri; Najar, Djeffal, Canouse, Smith; Robertha, Estrada
Bayern Munich possible starting lineup:
Neuer; Mazraoui, Upamecano, Hernandez, Davies; Kimmich, Goretzka; Gnabry, Muller, Coman; Mane
We say: DC United 0-5 Bayern Munich
Bayern could hardly have been handed a friendlier post-Lewandowski opening fixture, and Nagelsmann's side still have plenty of world-class attackers ready to steal the spotlight.