Slight soda taste

My second batch of extract beer has aged almost 3 weeks in the bottle. I started drinking them, but I notice they have a slight soda aftertaste. It seems like they have a lot of carbonation at first, but then it sort of disappears. Any ideas for the cause? I've done a lot of searching on the forums, but I can't find an answer to this.

I cleaned everything with either bleach or Oxi Clean, rinsed thoroughly, sanitized with Easy Clean. The brew fermented for 2 weeks in the primary, and I used the specified amount of priming sugar.

What do you mean by a slight soda aftertaste? Sweet?

That usually happens when you underhop or the beer wasn't done fermenting when you bottled.

You mentioned 2 weeks in the primary, but that's it. Did you do a secondary? How long?

Carbonation/head will usually disappear quickly if there is soap residue on the glasses. This includes a film when using a streak-free soap in dishwashers.