Is my mixing barrel clean or not?

[Gunsnroses]

I cut the tops out of my mixing barrels today so I could clean the stuff out of the inside. These are the white food grade barrels you get from your local CO-OP. Mine had Mountain Dew syrup residue in them.
I filled the 1/4 of the way with tap water and put a half gallon of Distilled White Vinegar in the barrel. Got down in there and wiped down the inside.
Rinsed the barrel and filled it 1/4 of the way again with tap water and then used dishwashing liquid. Wiped down the inside thoroughly and rinsed.
Then filled the barrel 1/4 way with RO-DI and wiped it down again.
Then towel dried.

It looks really clean, but I can still smell the Mountain Dew syrup.
I dont mind the smell, but I dont want to contaminate my RO-DI water I will be using to mix salt with.
I know alot of you have used these type barrels before, so is this normal?
Is the smell going to be there and the water be o.k. to use?

Or, if I can smell the Mountain Dew smell, does that mean my barrel is not clean and not ready for RO-DI water?

[DEFCLONE80]

I had the same issue with a barrel that was used with green olives. I had the same fear because I could not remove the smell. I know there is a big difference between olives and mt dew. After a few salt mixing the smell will go away. If you are still unsure give it a couple more washes.

[bnumair]

after a good vinegar bath i dont see an issue. material should be food safe grade as mtndew syrup was kept in it.

[Gunsnroses]

It seems really clean. The barrel is so white on the inside that it makes the tap water look blue. Lol
I just wanted to make sure that nothing harmful was going to leach out over time.
I knew a lot of people used these types of barrels, so I thought some would chime in and give their experience on the subject.