Didn't add enough water

I’m making a 2.5 gallon batch of pale ale. After 2 weeks in the fermenter, I realized that I had added only enough water to get to 2 gallons (rather than 2.5).
Any suggestions for getting to that 2.5 amount that I want?

I think an easy fix would be, assuming you are bottling this, mixing your priming sugar with a half gallon of water, bring to boil like usual, and procede as usual. I have done this before on a smaller scale when I have undershot on the water all grain.

Taste your hydrometer samples for FG. You may decide not to add back the full one-half gallon. Here is a dilution calculator which may help in decision making.

Neat tool. Bookmarked, and better than guesstimating!

Tasted it. Tasted it again (just to make sure). My 3rd taste, which was in a larger glass, confirmed that I was a bit low. So I used a quart of water for my priming solution rather than the usual cup.