sfetch: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On Debian possible default full paths are:

/usr/bin/sfetch - from package: biosquid

You may install the required package with command apt-get install {package}

Error in other languages:
sfetch: bevel nie gevind nie
sfetch: comandă negăsită
sfetch: comando não encontrado
sfetch: commande introuvable
sfetch: command not found
sfetch: käsku ei ole
sfetch: không tìm thấy lệnh
sfetch: komanda nerasta
sfetch: Kommando nicht gefunden.
sfetch: kommandot finns inte
sfetch: komut yok
sfetch: nie znaleziono polecenia
sfetch: níor aimsíodh an t-ordú
sfetch: no se encontró la orden
sfetch: no s'ha trobat l'ordre
sfetch: opdracht niet gevonden
sfetch: parancs nem található
sfetch: perintah tidak ditemukan
sfetch: príkaz nenájdený
sfetch: příkaz nenalezen
sfetch: команда не найдена
sfetch: командата не е открита
sfetch: 命令找不到
sfetch: コマンドが見つかりません