All of the above.
Glucose is water soluble, so a good soak with plenty of water will get rid of it.
Make sure you rinse it out well and you will be fine.
I bought a new IBC the first time because I was worried about contamination, but when I needed a second one I bought one that had had some sort of PVA glue in it. I washed it out with a hosepipe a few times then used it. The pure water I put in it stayed pure.
Whatever they've had in before, if you give them a good wash out they will be fine.