Filling and supplying with 'di' instead of 'with'
Italian has a group of verbs about filling, flooding or equipping something. They all work the same way: the thing that gets filled or equipped is the direct object, and the contents come after di. So you fill a glass di water, flood a room d'acqua, and supply someone di tools. Verbs like riempire, fornire, inondare and gonfiare all follow this pattern.
English uses with here: fill it with water, provide them with tools. Learners therefore tend to translate word for word and reach for con. Sometimes that is understandable, but di is the natural, default choice. Once you notice it, you will see it everywhere.
The structure is: verb + container (direct object) + di + contents. Think of di here as meaning full of or made up of, not as together with. That is the same di you find in pieno di (full of) and coperto di (covered with).
Before a vowel, di often shortens to d', which is very common with acqua, aria and olio:
The contents usually come without an article when you mean an unspecified amount: di acqua, di libri, di messaggi. The pattern also survives in the passive and in the past participle used as an adjective:
Riempire is the everyday verb for filling something. It works with bottles and buckets, and also with time, pages or rooms.
Inondare means to flood, literally or figuratively. The figurative use is very common for messages, light or emotions.
Gonfiare means to inflate, so the contents are usually air or gas.
Fornire means to supply or provide. Here the container is a person or place, and di introduces what they receive.
Other verbs work the same way: dotare (to equip), munire (to furnish, to arm), imbottire (to stuff, to pad) and caricare in the sense of loading a car or truck: caricare la macchina di valigie.
Fornire has a second construction: the thing supplied becomes the direct object and the person gets a. Both are correct, so pick one and do not mix them.
A typical mistake is fornire a qualcuno di qualcosa, which blends the two patterns. Say either fornire qualcuno di qualcosa or fornire qualcosa a qualcuno.
You will also hear con with riempire when the focus is on the tool or method, as in riempire il buco con il cemento (fill the hole using cement). For plain contents, di sounds more natural.
Finally, circondare (to surround) can take di when someone does the surrounding on purpose, as in circondarsi di amici (to surround yourself with friends), but in the passive it usually takes da: una casa circondata dagli alberi.
With verbs of filling, flooding, inflating or supplying, put the container or receiver straight after the verb and introduce the contents with di: riempire la bottiglia d'acqua, fornire gli studenti di libri. Where English says with, Italian usually says di.