SIM for Germany and Czech

[inquisitor]

If you activate the 500MB data option (so-called "Handy-Internet-Flatrate") which costs € 9.99 for Fonic or € 6.95 for Lidl data roaming in the EU will cost € 3 per calendar day but you will only have 10MB per day after which the connection will be interrupted.
With all other data options (even including the larger 5GB data option offered by Lidl) Internet access in the EU will be billed with € 0.83/MB (billed in 1KB increments).