What would be the most natural translation of this phrase "might as well"?
I think depending on the context, there may be more than one way to say it in Hindi. We can use, "bhi" or "hi" to mean the same or in some other ways too. For example:
"Since you have to wait, you might as well sit down and relax."
"Tumhe pratiksha karni hi hai, to tum baith bhi sakte ho aaraam se." (तुम्हें प्रतीक्षा करनी ही है तो तुम तुम आराम से बैठ भी सकते हो.)
OR
"Jab tumhe pratiksha karni hi hai to kyon na baith jao, thoda aaraam kar lo?"
OR
"Chunki tumke pratiksha karni hai, achchha hoga yadi tum baith hi jaao"
Word reference: might as well, hindi