#C (gcc), 69 62 50 bytes

Saved 12 bytes, thanks to ErikF's suggestion:

f(char*s){for(printf("!");*s;)printf("%c!",*s++);}

Try it online!

C (gcc), 69 62 50 bytes

Saved 12 bytes, thanks to ErikF's suggestion:

f(char*s){for(printf("!");*s;)printf("%c!",*s++);}

Try it online!

#C (gcc), 69 62 50 bytes

Saved 12 bytes thanks to ErikF's suggestion.

f(char*s){for(printf("!");*s;)printf("%c!",*s++);}

Try it online!

#C (gcc), 69 62 50 bytes

Saved 12 bytes, thanks to ErikF's suggestion:

f(char*s){for(printf("!");*s;)printf("%c!",*s++);}

Try it online!

#C (gcc), 69 62 50 bytes

• Saved 12 bytes thanks to ErikF's suggestion.

  f(char*s){for(printf("!");*s;)printf("%c!",*s++);}

Try it online!

#C (gcc), 69 62 50 bytes

Saved 12 bytes thanks to ErikF's suggestion.

f(char*s){for(printf("!");*s;)printf("%c!",*s++);}

Try it online!